There is conventionally known a partition-type heat exchanger having an object to apply a treatment such as heating of an object to be heated, phase transformation or a reaction by arranging a heating gas on one side of the partition and the object to be heated on the other side, and causing the heat from the heating gas to transfer through the partition to the object to be heated.
For example, the "CERAMIC HEAT EXCHANGER CONCEPTS AND TECHNOLOGY", (NOYES PUBLICATIONS, 1985) discloses various partition-type heat exchangers for heat exchange between gases (hereinafter referred to as the "prior art 1"). More specifically, a partition-type heat exchanger disclosed in the prior art 1, is of the finned plate type, the tube in shell type, the tube in tube type or the helical type in terms of the structure, and the material of the partition comprises codielite (2MgO/2Al.sub.2 O.sub.3 /5SiO.sub.2), magnesia-alumina silicate and silicon carbide. Such a ceramic partition suffers from quality deterioration during a long-term use, leading to occurrence of cracks. Further, when cracks grow into through-cracks, a gas on the high-pressure side leaks through the partition to the low-pressure side, thus making the partition inapplicable. The prior art 1 describes no method for repairing through-cracks occurring in the partition. In the aforementioned heat exchanger, therefore, a damaged partition is conjectured to be abandoned.
A coke oven is a furnace for manufacturing coke through dry distillation of coal, and serves also as a heat exchange between a gas and a solid. In the coke oven, there are alternately arranged carbonization chambers into which coal is charged and combustion chambers for generating a heating gas via partitions. First, the partition is heated by the heating gas. Then, heat is transferred, via the partition, to the coal charged in the carbonization chamber. The coal is thus pyrolysed, and dry distillation proceeds. Silica bricks are usually used for the aforementioned partition. Further, Japanese Unexamined Patent Publication No. S52-91,001 discloses use of a partition comprising silica carbide bricks. The partition has generally a thickness within a range of from 50 to 150 mm.
Finished high-temperature coke upon the completion of dry distillation is discharged by an extruder from the extruding side to the coke side after removal of covers on the extruding side and the coke side. Then, coal of the next charge at the room temperature is charged through a coal charging port provided at the top, and the aforementioned process is repeated. The partition is shaven by the extruded coke. Repetition of heating and cooling causes joint breakage between bricks or a cracking damage to the bricks. When a cracking damage becomes larger as to run through the carbonization chamber and the combustion chamber, a dry distillation gas containing aromatic hydrocarbon leaks from the carbonization chamber into the combustion chamber, making it difficult to continue dry distillation of coal. To avoid this inconvenience, it is the usual practice to repair the above-mentioned cracking damage.
For the purpose of repairing, there is known a method of pneumatically transporting a refractory powder to an empty carbonization chamber and filling a through-crack with the refractory powder. This method, although permitting temporary reduction of gas leakage, does not ensure reinforcement of bricks, with the gas leakage reducing effect not lasting long. This is attributable to the fact that the refractory powder accumulated at the through-crack shrinks as sintering proceeds, leading to production of voids, and then, the gas flowing from the voids causes scattering of sintered pieces, thus causing again expansion of cracks. When, upon filling the through-crack with the refractory powder, the powder passes through the through-crack, reaches the combustion chamber on the other side and accumulates there, it is difficult to remove accumulation of powder from the combustion chamber. If no action is taken against this defect, a problem occurs in that the combustion space becomes smaller, leading to a lower combustion performance.
Another known method for repairing the oven wall near the oven cover is the wet spraying method of spraying a mixture of a refractory powder and water to the damaged portion. Because a prescribed strength of refractory is unavailable in this method, the refractory tends to easily peel off upon occurrence of only a slight shock. This method is therefore only a temporary measure.
The flame spraying method is also known as a repairing method of a partition. The partition is shaven by coke extruded after dry distillation or damaged by thermal spalling, and surface irregularities occur on the wall surface on the carbonization chamber side in the long run. As a result, the pressure acting on the extruder of coke increases, and under some circumstances, extruding is made impossible. In such a case, the partition is repaired by the flame spraying method with a view to preventing the surface irregularities from becoming excessive.
Repairing by the flame spraying method is accomplished by bringing a refractory powder into a semi-molten state or a molten state through a flame comprising oxygen and a fuel gas, or combustion of aluminum and silicon, thereby causing the refractory powder to adhere to the damaged portion of the partition. For example, Japanese Patent Publication No. S62-15,508 discloses a flame spraying material applicable for such a purpose (hereinafter referred to as the "prior art 2"). Japanese Patent Publication No. H03-9,185 discloses a high-silica flame spraying material comprising SiO.sub.2, Al.sub.2 O.sub.3, CaO, Fe.sub.2 O.sub.3 and Na.sub.2 O in specific percentages for forming a spray-repairing material applicable in a long-term use (hereinafter referred to as the "prior art 3"). Upon application, the aforementioned spraying material is melted by flame, hits the portion to be repaired, rapidly cooled for solidification there, and thus forms spray-repaired portion mainly comprising a glass phase. The above-mentioned glass phase further transfers to a crystalline phase during the course of cooling. At this point, volumetric shrinkage occurs in the glass phase, thus causing cracks. This leads to an insufficient bonding between the spray-repaired portion and the substrate, so that the spray-repaired portion cannot withstand a long use. Particularly when the substrate suffers from quantity degradation to a lower strength, cracks propagate from the substrate side, causing dropping of the spray-repaired portion. For applying this method, furthermore, it is necessary to previously specify the damaged portion. However, portions capable of being observed from outside are limited to portions near the cover on the extruding and coke sides. Observation of inner portions is very difficult. This method has therefore a problem of difficulty in applying to the interior of the carbonization chamber.
When there is a serious damage to the silicate bricks forming the partition, the damaged bricks are relined. With a view to avoiding a damage resulting from cooling of the remaining bricks, relining is carried out in hot. Japanese Unexamined Patent Publication No. H05-132,355 discloses a silica brick for repairing in hot excellent in thermal spalling resistance and wear resistance, for use in relining-repairing in hot of partition bricks of a coke oven (hereinafter referred to as the "prior art 4"). However, repairing operations in hot requires heavy muscular work at high temperatures, and further, leads in stoppage of coke production for a long period of time, thus resulting in a serious economic loss.
As described above, the conventional methods involve many problems to be solved. From among the conventional methods, the flame spraying method is excellent in operability and economic merits. The spray-repaired portion, being relatively satisfactory in wear resistance and durability, is not as yet sufficient. The service life of the spray-repaired portion is not determined by the strength and spalling of the spray-repaired portion itself alone, but the flame spraying method still involves the aforementioned problem of dropping of the spray-repaired portion, so that it cannot be used for a long period of time, leading to a service life of only about six months.
In a partition for a partition-type heat exchanger, for example, a partition between a carbonization chamber and a combustion chamber in a coke oven, and essential requirement is that a through-crack running from a carbonization chamber to a combustion chamber is not present in, for example, a coke oven, and a smooth wall surface should preferably be maintained. It is therefore important to improve strength and wear resistance of the partition. When a through-crack occurs in the partition, however, it is necessary to conduct a replacement of the damaged portion of the partition or a repair by the flame spraying method. When replacing the damaged portion, as described above, the apparatus operation must be discontinued for a long period of time. In an equipment in which it is substantially impossible to cool the oven for protecting the partition, such as a coke oven, there is a problem that the partition must be exchanged in hot. Further, in order to carry out a replacement of the partition or flame spraying onto the damaged portion of the partition, it is necessary to preciously specify the damaged portion, and a problem is that the replacement must be carried out in hot presenting a severe working environment.
The present invention has therefore an object is to solve the above-mentioned conventional problems, and to provide a method for repairing and/or reinforcing a partition of a partition-type heat exchanger, which permits repairing of damage such as cracks and surface irregularities occurring in the partition as in the conventional art through clogging of gas flow and formation of a smooth flat surface, and at the same time, enables to improve strength and wear resistance of the partition itself.